Lighting apparatus for incorporation into walls, panels, ceilings, floors or similar structures

ABSTRACT

A lighting apparatus ( 10 ) is described for incorporation into a tiled wall, panel, ceiling, floor or similar structure ( 38,40 ). The apparatus comprises: a reflector unit ( 12, 14 ) that has at least one reflective surface ( 24, 26 ) for location behind the surface of the structure and an external light-transmissive face ( 14 ) for location generally flush with the surface of the structure; and means ( 28 ) for coupling an end of a fibre-optic cable ( 32 ) having a multiplicity of optical fibres ( 34 ) to the reflector unit behind the surface of the structure so that light projecting from the ends of the fibres enters the reflector unit and is reflected by the reflective surface(s) so as to provide substantially uniform illumination across the light-transmissive face. The reflector unit is formed with an external flange ( 20 ) generally parallel to the light-transmissive face. This facilitates positive fixing of the apparatus to the substrate of the wall or ceiling, for example using tile cement, and enables repositioning of the apparatus and surrounding tiles until the cement is dry.

This invention relates to lighting apparatus for incorporation intowalls, panels, ceilings, floors or similar structures. The invention wasoriginally conceived to provide a decorative lighting effect in a tiledwall or ceiling, but it may be applied to other structures, and it maybe used for other purposes, for example direction indication.

Lighting apparatus typically uses an electric light bulb or tube as asource of light, and there is a need to be able to replace the lightbulb easily when it blows. In the case where the lighting apparatus isemployed in a wet or damp environment (such as outdoors, in the wall orbottom of a swimming pool, or in the wall or ceiling of a showercubicle), there is a need to insulate any high-voltage electrical supplyfor the apparatus from the wet or damp environment. To deal with theseneeds, it is known to use a fibre-optic cable to transmit light from thelight source (which may be in a dry and easily-accessible location) tothe light outlet. This invention employs such a technique, and theinvention relates more particularly to a lighting apparatus forincorporation into a wall, panel, ceiling, floor or similar structure,the apparatus comprising: a reflector unit that has at least onereflective surface for location behind the surface of the structure andan external light-transmissive face for location generally flush withthe surface of the structure; and means for coupling an end of afiber-optic cable having a multiplicity of optical fibres to thereflector unit behind the surface of the structure so that lightprojecting from the ends of the fibres enters the reflector unit and isreflected by the reflective surface(s) so as to provide substantiallyuniform illumination across the light-transmissive face.

Such an apparatus is known and takes the form of an illuminated blockintended to be incorporated into a block-paved path laid on a sand ormortar base. The thickness of the illuminated block and the othernon-illuminated blocks might typically be 3½″ (90 mm). The fibre-opticcable, which might typically have an external diameter of about ¾″ (20mm), enters the centre of one side of the illuminated block. To allow anadjacent one of the non-illuminated blocks to butt up against that sideof the illuminated block, the adjacent block has a notched underside.The fibre-optic cable is curved downwardly in the notch, and then passesunder other blocks of the path by being embedded in the sand or mortarbase.

A first aspect of the invention is concerned with providing an apparatusthat (a) can be incorporated into a block arrangement, but that does notrequire an adjacent block to be notched to receive the fibre-opticcable, and (b) can readily be used with thinner blocks than mentionedabove, for example floor, wall or ceiling tiles having a thickness ofperhaps ¼ to ½″ (6 to 13 mm).

The apparatus of the first aspect of the invention is characterised inthat the coupling means is arranged to locate the ends of the fibres sothat their overall cross-section is as a ribbon, for example in a singlerow or relatively few rows. In the case of, for example, a tiled wall,because of the thinness of the ribbon cross-section, the optical fibrescan be embedded unnoticeably in the adhesive by which an adjacent tileis affixed to the wall. Also, in the case of, for example, a tiled oruntiled plasterboard wall having restricted space behind theplasterboard, the ribbon cable can be more readily fed through therestricted space. Furthermore, the ribbon configuration can be used tofacilitate obtaining uniform illumination across the light-transmissiveface of the apparatus, because the light enters the reflector unit as aband, rather than a spot, of light.

Preferably, the depth of the reflector unit behind the surface of thestructure is substantially less than (for example less than one half ofand more preferably less than one third of) any dimension of thelight-transmissive face across the face. More preferably, the depth ofthe reflector unit is such that when fitted into a plasterboard or MDFpanel having a thickness of, say, ½″ (12 mm), it does not protrudebehind the rear face of the panel. This enables the apparatus to be usedin, for example, a plasterboard wall without the need to excavatewhatever may be behind the plasterboard, such as another sheet ofplasterboard in the case of an internal wall, or a layer of bricks orblocks in the case of an external wall.

In one embodiment, the reflector unit comprises a solid block oflight-transmissive material, one surface of the block providing thelight-transmissive face, at least one other surface of the blockproviding the reflective surface(s) by internal reflection within theblock, and a further surface of the block being arranged to receivelight from the ends of the optical fibres.

In the known apparatus described above for providing an illuminatedblock in a block-paved path, the apparatus simply rests on the sand ormortar base, and non-illuminated blocks butt up against it on all foursides. However, if lighting apparatus of this generally type is to beused in a tiled wall or ceiling, it is necessary to provide morepositive fixing of the apparatus to the substrate of the wall orceiling, and a second aspect of the invention is concerned with this.

The lighting apparatus of the second aspect of the invention ischaracterised in that the reflector unit is formed with an externalflange generally parallel to the light-transmissive face.

The flange may lie behind the light-transmissive face and preferably berelatively thin. In this case, when the apparatus is to be affixed to,for example, a plasterboard wall, a hole can be cut in the plasterboardto receive the apparatus, the rear of the flange can be cemented to theplasterboard around the hole, and other tiles can be laid over theflange and around the light-transmissive face.

In one embodiment, the reflector unit may comprise: a hollow box, thebox having at least one wall providing the reflective surface(s), anopening arranged to receive light from the optical fibres, and an openside; and a light-transmissive plate closing the open side of the boxand providing the light-transmissive face. In this case, the apparatuspreferably further includes a light-transmissive element extendingacross and sealing the opening, and the light-transmissive platepreferably seals the open side of the box. Moisture, debris and insectscan therefore be kept out of the box. In this case, the flange mayprovided by a marginal edge of the light-transmissive plate extendingbeyond the sides of the box. When the apparatus is to be affixed to, forexample, a plasterboard wall, a hole can be cut in the plasterboard toreceive the reflector box, the rear of the flange can be cemented to theplasterboard around the hole, and other tiles can be laid around andbutt up against the edges of the light-transmissive plate.

A mounting frame may also be provided having an opening sized and shapedto receive the outline of the reflector unit behind the flange. Theframe is preferably relatively thin and can be sandwiched and cementedbetween the substrate of the wall or ceiling. The frame enables the holethat is cut in the substrate to receive the apparatus to be cut oversizeto allow fine positioning of the apparatus and/or to be cut roughly, andyet enables to apparatus to be firmly secured to the substrate.

In accordance with a third aspect of the invention, there is provided awall, panel, ceiling, floor or similar structure having: a substrate; alighting apparatus according to the first or second aspect of theinvention embedded in the substrate; an arrangement of tiles affixed tothe substrate and surrounding and generally flush with thelight-transmissive face; a fibre-optic cable having a multiplicity ofoptical fibres coupled at one end to the coupling means; and a lightsource for shining light into the other end of the fibre-optic cable.

In accordance with a fourth aspect of the invention, there is provided apanel having: a hole therethrough; a lighting apparatus according to thesecond aspect of the invention mounted behind the panel and having thelight-transmissive face filling the hole, the front face of the flangeor frame being secured to the rear of the panel around the hole; afibre-optic cable having a multiplicity of optical fibres coupled at oneend to the coupling means; and a light source for shining light into theother end of the fibre-optic cable.

Specific embodiments of the present invention will now be described,purely by way of example, with reference to the accompanying drawings,in which:

FIG. 1 is an exploded isometric view of a first embodiment of lightingapparatus;

FIG. 2 is a rear view of the apparatus of FIG. 1;

FIG. 3 is a plan view of the apparatus of FIG. 1;

FIG. 4 is a sectioned side view of the apparatus of FIG. 1 incorporatedinto a tiled wall having a plasterboard substrate;

FIG. 5 is similar to FIG. 4, but showing a modified path for thefibre-optic cable;

FIG. 6 is similar to FIG. 4, but showing another modified path for thefibre-optic cable and a modified light transmissive plate;

FIG. 7 is an isometric view of a second embodiment of lightingapparatus;

FIG. 8 is a sectioned side view of the apparatus of FIG. 7 incorporatedinto a tiled wall having a plasterboard substrate;

FIG. 9 is an exploded isometric rear view of a third embodiment oflighting apparatus;

FIG. 10 is a sectioned side view of the apparatus of FIG. 9 incorporatedinto a tiled wall having a plasterboard substrate;

FIGS. 11A-B are isometric views of the elements of a modified lighttransmissive plate;

FIGS. 12A-E are a plan view, a view of one end, a view of the other end,a side view and a sectioned plan view of a modified plug for connectingthe fibre-optic cable to the lighting apparatus;

FIG. 13 is an isometric view of jig to facilitate insertion of theoptical fibres into the plug; and

FIG. 14 is similar to FIG. 13, but showing the jig in use.

Referring to FIGS. 1 to 4, the first embodiment of lighting apparatus 10comprises a reflector box 12 and a light-transmissive front plate 14.The reflector box 12 is moulded from plastics material, but may be madein any other suitable manner from any other suitable material. In theexample shown, the front plate 14 is square and is made of clear orcoloured frosted glass or plastics material that has a relatively hightransmittance to at least some colours of visible light, but whichobscures any detail being seen through the plate 14.

The reflector box 12 has: a square open front 16 surrounded by arabbeted lip 18; a planar external flange 20 behind the lip 18 andsurrounding the open front 16; a top wall 22 and a pair of side walls 24behind the flange 20; and a rear wall 26 that extends between the rearedges of the side walls 24 and from the rear edge of the top wall 22 tothe lower portion of the rabbeted lip 18. The rear edges of the sidewalls 24 are curved so that the rear wall 26 is part-cylindrical andconcave, as seen from inside the box 12. The depth D of the box 12behind the rear face of the flange 20 is preferably about ½″ (12 to 13mm). The top wall 22 is formed along almost its entire length with ashouldered slot 28, and the bottom of the slot 28 is covered by a strip30 of clear glass or plastics material cemented into a complementaryrecess in the lower face of the top wall 22.

The light-transmissive front plate 14 is dimensioned so that it is asnug fit in the rabbet of the lip 18, and it is cemented in place sothat the plate 14 and the strip 30 seal the box 12 against the ingressof water, condensation, insects and other material.

The inner surfaces of the walls 22,24,26 of the box 12 are highlyreflective to visible light, for example by being coated with a shinymetallic film, lined with a shiny metallic foil or by being white. Inuse, light is introduced into the box from a light source (not shown)via a fibre-optic cable 32. The light source is installed in an easilyaccessible and dry location. The light source may produce white light,or light of any desired colour, and it may be arranged to change thecolour of light periodically. At least at the box end of the cable 32,the optical fibres 34 of the cable are arranged side-by-side in a singlerow, or relatively few rows, as a ribbon. The ends of the optical fibres34 are secured into a male connector plug 36 that is fitted into theslot 28 in the top wall 22 of the reflector box 12 so that the ends ofthe optical fibres 34 point in a direction parallel to thelight-transmissive plate 14. The plug 36 may be held in the slot 28 by afriction fit, assisted possibly by a sealing ring (not shown) and/or bya latching mechanism (not shown). The light that is shone into the box12 reflects off the walls 22,24,26 of the box 12 and may partiallyreflect off the inner surface of the plate 14, and is transmittedthrough the plate 14 so that from the outside the plate is illuminatedwith a generally uniform light distribution.

The apparatus of FIGS. 1 to 4 is intended to be installed amongst anarray of tiles 38 cemented to a plasterboard wall 40. Duringinstallation, a hole (as shown in dash-dot lines 42 in FIG. 2) is cut inthe plasterboard wall 40, and the fibre-optic cable 32 is fed behind thewall 40 to the hole 42. The plug 36 is fitted into the slot 28, and thebox 12 is fitted into the hole 42 and held roughly in position by cement44 between the wall 40 and the rear faces of the side and lower portionsof the flange 20. The surrounding tiles 38 are then cemented in placewith their edges adjacent the box 12 overlapping the flange 20, and withthe face of the plate 14 flush with the faces of the surrounding tiles38. The positions of the box 12 and tiles 38 are finely adjusted beforethe cement sets.

FIG. 5 shows a modification to the above, in the case where it is notpossible to feed the fibre-optic cable 32 behind the wall 40. In thiscase, the fibre-optic cable 32, in its ribbon form and with a protectivesleeve or other covering, is embedded in the cement 44 that is used tohold the tiles 38 in place.

FIG. 6 shows a modification to the above, in the case where there ismore room to feed the fibre-optic cable 32 behind the wall 40. In thiscase, for most of their run, the optical fibres 34 of the cable arebound in a twisted formation in a circular cross-section sheath 46 thatenables the cable 32 to be curved more easily in various directions. Thesheath 46 terminates shortly before the ends of the optical fibres 34,and the fibres 34 are splayed out into the ribbon form and held in theplug 36. In order to prepare such an end of the cable 32, the sheath 46is cut back the required amount. The fibres 34 are then insertedside-by-side into an elongate U-shaped jig 100, as shown in FIGS. 13 and14, resembling a hair-grip with a spacing between the tines 102 of thejig 102 being only slightly larger than the diameter of each fibre 34.The ends of the fibres 34 are then inserted into the plug 36 and gluedin place, for example with cyanoacrylate (superglue). Once the glue isset, the jig 100 is removed, and the ends of the fibres 34 are trimmedflush with the plug 36. The plug 36 may alternatively be made in twoportions that are fastened together and hold the fibres in place due tothe fastening pressure.

FIG. 6 also shows a modification in which the lip 18 is bevelled, ratherthan rabbeted, and a complementary bevel 48 is provided on the inneredges of the light-transmissive plate 14. This enables a smaller a gapbetween the plate 14 and the surrounding tiles 38.

The second embodiment of lighting apparatus 50 will now be describedwith reference to FIGS. 7 and 8. The second embodiment is similar to thefirst embodiment except in the following respects.

Instead of employing a hollow box 12 closed by a light-transmissiveplate 14, the apparatus 50 has a thicker block 52 of light-transmissivematerial that is bonded to a housing 54 having a rear wall 56 coveringthe rear face of the block 52, side walls 58,60 and a bottom wall 62partially covering the side and bottom edges of the block 52, and athicker top wall 64 partially covering the top edge of the block 52. Thefront edges of the side and bottom walls 58,60,62 are flanged andprovide, in combination with the front edge of the top wall 64, a planarexternal flange face 20 encircling the edges of the block 52. The topwall 64 is formed with the shouldered slot 28 to receive the plug 36 atthe end of the fibre-optic cable 32. Before being bonded in the housing54, the rear face and the edges of the block 52 are silvered, painted orcoated white, or otherwise treated so that they are totally reflective.

The apparatus 50 of FIGS. 7 and 8 is installed in much the same way asthe apparatus 10 of FIGS. 1 to 6, with the rear surfaces of the side andbottom portions of the flange 20 being cemented to the plasterboard 40,and with the surrounding tiles 38 overlapping the front surface of theflange 20 and butting up against the edges of the light transmissiveblock 52.

The third embodiment of lighting apparatus 70 will now be described withreference to FIGS. 9 and 10. The third embodiment is similar to thefirst embodiment except in the following respects.

In FIGS. 9 and 10, the light-transmissive plate 14 is bonded to thefront edge of the reflector box 12, so that the marginal edges of theplate 14 project beyond the outline of the reflector box 12 to form aflange 72. The reflector box 12 has upper and lower walls 74,76 havingarcuate rear edges, and the rear wall 78 of the reflector box 12 ispart-cylindrical, following the lines of the rear edges of the upper andlower walls 74,76. The inner surfaces of the upper, lower and rear walls74,76,78 are reflective. The upper wall 74 is formed with an opening 80to receive the end of the circular cross-section optical-fibre cable,and the opening is sealed by a disc 82 of clear glass or plasticsmaterial. The apparatus 70 also includes a mounting frame 84 formed froma rectangle of thin sheet material, which may be meshed, having acentral rectangular hole 86 that is a snug fit around the outline of thereflector box 12 immediately behind the flange 72.

During installation of the apparatus 70, a hole 42 is cut in theplasterboard wall 40 that is larger than the hole 86 in the frame 84 butsmaller than the outline of the frame 84. The frame 84 is fitted to thereflector box 12, and the rear of the reflector box is fitted into thehole 42 with the end of the fibre-optic cable 32 fitted into the opening80. The frame 84 is held roughly in position against the wall 40, andthe box 12 is held roughly in position in the frame 84, by cement 44.The surrounding tiles 38 are then cemented in place with their edgesadjacent the box 12 overlapping the frame 84, and with the front face ofthe plate 14 flush with the faces of the surrounding tiles 38. Thepositions of the box 12 (and frame 84) and tiles 38 are finely adjustedbefore the cement sets.

Many modifications and developments may be made to the embodiments ofthe invention described above. For example, the light-transmissive plate14 or block 52 need not be square or rectangular, but may be a morecomplex regular or irregular shape, in which case the reflector box 12or housing 54 may be shaped complementarily, and the plug 36 may also beshaped to follow the outline of part of the shape, with the ends of theoptical fibres 34 being trimmed accordingly. Alternatively, in order toobtain a similar effect, and as shown in FIG. 11A, thelight-transmissive plate 14 or block 52 may be formed in two parts 90,92 that are UV-bonded together. One part 90 has a square or rectangularshape to fit the reflector box 12 or housing 54. The other, front, part92 is cut to the required visible shape (which is shown as an octagon inthe FIG. 11A but may be any desired shape). One of the tiles 94 of thetype that will surround the apparatus is cut, for example using a waterjet cutter, with a hole 96 to match the shape of the shaped part 92, asshown in FIG. 11B. During installation, the tile 94 is cemented to thepart 90 so that the part 92 fills the hole 96, and so that in use thepart 92 is illuminated, but the tile 94 is not, due to its opaqueness.Alternatively, the part 92 may be of one colour, and the tile 94 may belight-transmissive and of a different colour.

In the embodiments shown in FIGS. 1 to 8, it may be desirable that theends of the optical fibres 34 projecting into the lighting apparatus10,50 are spaced apart from each other, rather than being contiguous. Inorder to achieve this, a modified plug 110, as shown in FIGS. 12A to 12Emay be employed. The plug 110 has a linear array of channels 112extending through it. At one end 114 of the plug 110, the channels arecontiguous, but they diverge through the plug 110, so that, at theopposite end 116 of the plug 110, they are spaced apart. At said one end114, the channels 112 are widened in the thickness direction of the plugso as to facilitate insertion of the optical fibres 34 into the plug110. Again, in order to fit the fibres 34 into the plug 110, the jig 100of FIG. 13 may be used to arrange the fibres 34 into a single contiguousrow, as shown in FIG. 14. Then, with the fibres 34 held in the jig 100,the ends of the fibres 34 are inserted into the widened portions of thechannels 112 at the end 114 of the plug 110 and pushed through thechannels 112, so that they protrude from the other end 116 of the plug110 in a spaced-apart configuration. Glue may be used to hold the fibres34 in position. The jig 100 is removed, and the projecting ends of thefibres 34 may be trimmed.

Although the examples of the invention have been described in thecontext of a tiled, plasterboard wall, the invention is also applicableto walls having other substrates, and to ceilings, floors, paths,prefabricated panels (for example for shower cubicles), etc. Theinvention can be used with a particularly pleasing effect in the wallsor bottom of a swimming pool. In the case where the apparatus is usedwith a panel, the front face of the flange 20 or frame 84 may be gluedor otherwise fastened to the rear face of the panel.

Whilst it may be desirable that the outer face of the light-transmissiveplate 14 or block 52 is perfectly flush with the surrounding tiles, insome cases it may be desirable that the outer face of thelight-transmissive plate 14 or block 52 is recessed slightly behind, orprojects slightly from, the surrounding tiles, and the term “generallyflush” used in this specification is intended to encompass suchvariations.

It should be noted that the examples of the invention have beendescribed above purely by way of example and that many othermodifications and developments may be made thereto within the scope ofthe present invention.

1. A lighting apparatus (10; 50) for incorporation into a wall, panel,ceiling, floor or similar structure (38,40), the apparatus comprising: areflector unit (12,14; 52,54) that has at least one reflective surface(24,26) for location behind the surface of the structure and an externallight-transmissive face (14; 52) for location generally flush with thesurface of the structure; means (28) for coupling an end of afibre-optic cable (32) having a multiplicity of optical fibres (34) tothe reflector unit behind the surface of the structure so that lightprojecting from the ends of the fibres enters the reflector unit and isreflected by the reflective surface(s) so as to provide substantiallyuniform illumination across the light-transmissive face; and, thecoupling means is arranged to locate the ends of the fibres so thattheir overall cross-section is as a ribbon.
 2. An apparatus as claimedin claim 1, wherein the coupling means is arranged to locate the ends ofthe fibres in a single row or relatively few rows.
 3. An apparatus asclaimed in claim 1, wherein the depth (D) of the reflector unit behindthe surface of the structure is substantially less than any dimension ofthe light-transmissive face across the face.
 4. An apparatus as claimedin claim 1, wherein the reflector unit (52,54) comprises a solid block(52) of light-transmissive material, one surface of the block providingthe light-transmissive face, at least one other surface of the blockproviding the reflective surface(s) by internal reflection within theblock, and a further surface of the block being arranged to receivelight from the ends of the optical fibres.
 5. An apparatus as claimed inclaim 1, wherein the reflector unit is formed with an external flange(20) generally parallel to the light-transmissive face.
 6. A lightingapparatus (10; 50; 70) for incorporation into a wall, panel, ceiling,floor or similar structure (38,40), the apparatus comprising: areflector unit (12,14; 52,54) that has at least one reflective surface(24,26) for location behind the surface of the structure and an externallight-transmissive face (14;52) for location generally flush with thesurface of the structure; means (28;80) for coupling an end of afibre-optic cable (32) having a multiplicity of optical fibres (34) tothe reflector unit behind the surface of the structure so that lightprojecting from the ends of the fibres enters the reflector unit and isreflected by the reflective surface(s) so as to provide substantiallyuniform illumination across the light-transmissive face; and, thereflector unit is formed with an external flange (20) generally parallelto the light-transmissive face.
 7. An apparatus as claimed in claim 6,wherein the flange lies behind the light-transmissive face.
 8. Anapparatus as claimed in claim 6, wherein the reflector unit (12,14)comprises: a hollow box (12), the box having at least one wall (24,26)providing the reflective surface(s), an opening (28) arranged to receivelight from the optical fibres, and an open side (16); and alight-transmissive plate (14) closing the open side of the box andproviding the light-transmissive face.
 9. An apparatus as claimed inclaim 8, further including a light-transmissive element (30) extendingacross and sealing the opening.
 10. An apparatus as claimed in claim 8,wherein the light-transmissive plate seals the open side of the box. 11.An apparatus as claimed in claim 8, wherein the flange is provided by amarginal edge of the light-transmissive plate extending beyond the sidesof the box,
 12. An apparatus as claimed in claim 8, further comprising amounting frame (84) having an opening (86) sized and shaped to receivethe outline of the reflector unit behind the flange.
 13. A wall, panel,ceiling, floor or similar structure having: a substrate (40); a lightingapparatus (10; 50; 70) embedded in the substrate; an arrangement oftiles (38) affixed to the substrate and surrounding and generally flushwith the light-transmissive face; a fibre-optic cable (32) having amultiplicity of optical fibres (34) coupled at one end to the couplingmeans; and a light source for shining light into the other end of thefibre-optic cable.
 14. A structure as claimed in claim 13, wherein thefibre optic cable extends as a ribbon between the substrate and at leastone of the tiles adjacent the light-transmissive face.
 15. A structureas claimed in claim 13, wherein a reflector unit is disposed in anopening (42) or recess in the substrate, and the rear of a flange isaffixed to the substrate around the opening or recess.
 16. A structureas claimed in claim 15, wherein the reflector unit (70) is disposed inan opening (42) or recess in the substrate, the mounting frame isdisposed between the rear of the flange and the substrate around theopening 15 or recess.
 17. A panel having: a hole therethrough; alighting apparatus (10; 50; 70) mounted behind the panel and having thelight-transmissive face filling the hole, the front face of the flangeor frame being secured to the rear of the panel around the opening; afibre-optic cable (32) having a multiplicity of optical fibres (34)coupled at one end to the coupling means; and a light source for shininglight into the other end of the fibre-optic cable.
 18. An apparatus asclaimed in claim 1, wherein one reflective surface of the reflector unitis opposite said external light-transmissive face of the reflector unit.19. An apparatus as claimed in claim 18, wherein one reflective surfaceof the reflector unit is smooth.
 20. An apparatus as claimed in claim18, wherein one reflective surface of the reflector unit is concave. 21.An apparatus as claimed in claim 18, wherein one reflective surface ofthe reflector unit is opaque.
 22. An apparatus as claimed in claim 1,wherein the light-transmissive face is smooth.
 23. An apparatus asclaimed in claim 4, wherein the block has first and second layers ofdifferent shapes.
 24. An apparatus as claimed in claim 8, wherein thelight-transmissive plate has first end second layers of differentshapes.